Great strides have been made in recent years in the field of oral health care. However, much remains to be done. While the development of anticaries agents, especially the fluorides, has led to a decline in the incidence of tooth caries it is desirable to even further decrease the number of teeth affected thereby. Moreover, attention in the oral health care field has increasingly focused on the problems of gum disease, periodontitis. While antibacterial agents have been proposed for inclusion in products for use by consumers in the treatment of periodontitis, certain problems have been associated with their use. For example, use of chlorhexidine, which has been known as as antibacterial agent, has been associated with staining problems. It produces yellow to dark brown stains on teeth, tongue and oral mucosa. Furthermore, chlorhexidine has a very bitter taste.
There has been a need, therefore, for developing a dentifrice formulation including antibacterial agents, which does not cause staining of the teeth and which has an improved taste. Moreover, dentifrices having improved anticavity effects are also desirable.
Staining can be troublesome, whether or not chlorhexidine is the cause. The accumulation of stains on tooth surfaces poses an esthetic problem for many individuals. Stains are usually extrinsic in nature and generally represent discolorations of the pellicle and/or plaque. The exact mechanisms involved in stain formation are still obscure. It has been suggested that pigments produced by chromagenic bacteria, colored products from the chemical transformation of pellicle components and adsorption/retention of dietary constituents contribute to extrinsic stain formation. The dietary factors which appear to contribute heavily to stain accumulation include coffee, tea, and red wines, as well as smoking. In addition to chlorhexidine, staining is promoted by cationic antimicrobial agents such as hexetidine or quaternary ammonium compounds.
Plaque is a common factor in caries, gum disease and staining and greatly contributes to their development. Proper oral hygiene as currently practiced requires that plaque be removed or prevented not only for cosmetic purposes but also to eliminate a source of potential injury to teeth and gums.
Dental plaque is initiated when cariogenic bacteria adhere to pellicle, the proteinaceous film on the surface of teeth. These adherent bacteria metabolize dietary constituents, reproduce and accumulate to form the tenacious deposit known as, plaque. Plaque generally consists of bacteria, bacterial end products such as polysaccharides, inorganic salts and salivary proteins. Plaque bacteria ferment dietary carbohydrates to organic acids which demineralize enamel, resulting in tooth decay.
Plaque acts as a nucleus for the formation of calculus (tartar) which is essentially plaque that has been mineralized with calcium phosphate salts. As calculus matures and hardens, it tends to stain noticeably due to adsorption of dietary chromagens: tea, coffee, smoke, etc. In addition to their unattractive appearance, calculus deposits, at the gum line, are a contributing source of gingivitis and periodontal disease.
Silicones have previously been suggested for inclusion in dentifrice compositions in that it has been expected that they would coat the teeth and thereby prevent cavities and staining. For example, British Patent Specification 689,679 discloses a mouthwash containing an organopolysiloxane for the purpose of preventing adhesion of, or for removal of, tars, stains, tartar and food particles from the teeth. However, polymers such as those disclosed in the '679 specification, have not generally been successfully used for coating the teeth since it has been found that the polysiloxane does not adhere to the teeth for prolonged periods of time. Therefore, the need for dentifrice formulations including a hydrophobic substance which effectively coats the teeth has not been satisfied.
Yetter U.S. Pat. No. 3,624,120 discloses quaternary ammonium salts of cyclic siloxane polymers which are said to be useful as cationic surfactants, as bactericides and as anticariogenic agents. Yetter indicates that it is believed that the siloxane polymer absorbs on calcium phosphate to form a film which decreases the rate of acid solubilization. However, due to the solubility of the cyclic, surface active, low molecular weight, high N/Si ratio compounds of Yetter, it would not be expected that they could impart a lasting, strongly hydrophobic film to the surface of teeth. Moreover, there does not appear to be any disclosure in Yetter that its low molecular weight compounds would have any usefulness in preventing staining. Other problems with the Yetter compounds are their high cost due to the high N/Si ratio. Also, the freedom from toxicity of high N/Si ratio compounds may be questioned.